Rotating vacuum seal



Feb. 14, 1950 J. J. vLAcH ROTATING VACUUM SEAL Filed June 7, 1946 2Sheets-Sheet 1 A @Ue/dior gy M /baya/jm @2v/Q 5 Feb. 14, 195o Filed June7, 194e 2 Sheets-Sheet 2 I a@ Q5 /A} 159 A 1 L a; Illll M60/k 27 J2 242JQ .52

:i "59 @a @y 'L Patentedv Feb. 14,1950

ROTATING VACUUM SEAL Jfohn J osephI Vlach, i Chicago, Ill., assignor fto vGeneral 'Electric :X-Ray ,Corporatiom Chicago, Ill., a corporationof New York v @marianne i., ma serial no, 615,048

Ther present invention vrelates in Ageneral to seals and sealing, andhas more particular referencel to the provision of means for sealingrotating, shaft-like members to prevent fluid leakage along the memberthrough a wall or journal in which the shaftextends; the inventionespecially relating to the sealing of low pressure vessels, such as vtheenvelopes of X-ray generators, particularly X-ray generators havingrotating anodes driven by motive means disposed'outward- 1y of theenvelope, 'wherein the anode and motive means are drivinglyconnected' bya shaft-like member extendingthrough'a wall portion of the envelope. n

Y X-ray generators commonly comprise an electron emitting cathode, and acooperative anode forming a target for receiving impingement .ofelectrons emitted from the cathode, X-rays being generated bysuch'electro'n impingeme'nt on the anode target. kThe anode and cathodeare commonly enclosed withina sealed 'and exhausted envelope, wherebythe anode aridcathodeelel ments may operate substantially in vacuo.' -Incertain circumstances, particularly in heavy duty generators, it isdesirable to utilize a rotating anode'positioned to receive electrons,atany instant, upon a portion onlyvof vthe anode target, said target being`of annular configuration, whereby, when rotated,l the target may becontinuously moved to progressively shift the portions thereof underelectronA bombardment, and, thus, prevent any target varea from becomingoverheated, it being understood Ythat electron bombardment results inthe, generation of excessive heat in the target element. -l

An important object of the present invention is to provide an improvedX-rayvgenerator having a rotating anode mounted within a sealed andevacuated envelope, together with facilities for driving the anode'frorn'outwardly of the envelope, by shaft-like means driving-ly connectedwith the anodean'd 'extending loutwardly of the envelope through a noveland'A eff'ective'shaftv seal formingA agportionof the'envelope.

Claims. (CL Z50- 148) v2 v Another important object lsv-to providearfshaft seal embodying Aan expansible'bellows element, carrying a 'sealfing adapted toforrn-a ground joint with a cooperating seal seat,wherebyisaid ringand seat may provide a vacuum sealwhen in relativerotation;'a furtherfobject beingto provide for the retention of a liquidsealing medium at, and on onel side of, said ground joint; a furtherobject beingto utilize the expansible bellows as a means for-retainingthe-liquid-v sealing medium at said'ground joint. i f.

Another important-object i to-provide vreservoir means for insuring themaintenance of liquid sealing medium at, and on one side of, the groundjoint;- a further object being vto Vregulate the. sup ply of liquidsealing medium toprevent leakage 'thereof through,theV grqundjoint andinto Athe evacuated vessel; 4 Another important object is to providev ashaft sealutilizing a liquidseal medium in comunetion With a seal ringand cooperating seat forming a running groundjoint'including the novelarrangement of'partsv whereby-the seal may be Y formed as a separateassembly unit, adapted for application upon -an envelope-or housing at ashaft opening therein, in position to sealingly cooperate With-a`shaft-like member extending in said opening, the particular arrangementof the seal 'making it` adaptable for use as avreplacement unit-,saidunit, when` mounted, forming a partof the envelope or housing on vWhich,itis-assembled. ..Another important objecty is to provide ar shaft sealfor the rotatingeanode of an X-ray generator, including sealed-meansforcirculating a cooling medium through the shaft to and from the anode ofthe generator, for thepurpose'of conf "tinuously cooling the .samewhile: the Vgenerator islin operation. i q f Y, p v f The foregoing andnumerous other important objects, advantages, and inherent functions ofthe inventionr Willbecome apparent as the'same is more fully understoodfrom the followingl description, which, .taken in connectionl with theaccompanying drawings, discloses a preferred embodiment of` theinvention. y

'Referringto `the-drawings: f.; ,t Fig. 1 isa sectional view througharr'X-ray generator embodying the present invention o Fig. 2 is anenlarged sectionalview ofa seal structure formlngfa part .of the deviceshown in Fig. l; and f Y iff f '.aFig. 3 is a modified seal arrangementembodying the invention. 'i1 i To, illustrate the invention, fthe.drawings show anzielcctronic device :comprising .ari X-ray igeneratorII, although it will be understood that the invention is not necessarilylimited, in all of its aspects, to X-ray generators, some of thefeatures of the present invention having general application wherevereffective shaft sealing functions are required. As shown on thedrawings, however, the generator I| may comprise sealed envelope meansI2 containing an anode I3 and a cooperating cathode I4 of any suitableor preferred construction The envelope I2 may be formed in anyconvenient or preferred manner, and may comprise any suitable envelopematerial. As shown, the envelope may comprise a tubular glass sleeve I5,having a re-entrant neck I3, at one end, upon which neck the cathodestructure I4 may be supported and sealed in any suitable fashion, as bymeans of the seal ring I'I, making an annular glass-to-metal seal withthe re-entrant neck IS. The opposite end of the envelope sleeve I5 may,likewise, be sealed upon the upstanding neck portion I3 of an annularflanged structure I9, the end of the sleeves I5 being sealed to the neckportion I8, as by means of a ring 20, similar to the ring I'I, andforming a glass-to-metal seal with the end of the sleeve I5.

The envelope I2 may, also, include closure means 2|, adapted forapplication to the flanged member I9 for sealing the openingtherethrough into the sleeve I5, said closure means 2| being epreferably formed to turnably support the anode I3. To this end, theclosure means 2| may include a preferably annular structure, comprisinga plate portion 22 formed with a central opening and adapted to beclamped sealingly with the flange structure I9, and a housing portion 23of preferably sleeve-like conguration adapted to form, with the plate 22and the flanged structure I9, a bearing cavity 24 extending axially of,and forming a continuation of, the space enclosed by the envelope sleeveI5.

The closure means 2| carries a bearing structure 25 within the chamber24, said structure being preferably mounted on a support spider 26disposed within the central opening of the plate portion 22. This spidermay conveniently be formed as an integral part of the plate portion 22.The housing portion 23 may extend outwardly of the plate portie-n 22,and may be formed with a seal seat 21 at the end thereof remote from theplate portion 22. This seal seat preferably dei'lnes `a central opening28 through which the shaft member 3|) extends. The flanged structure Itand, also, the closure means 2| may be made of any suitable, preferablymetallic material, and may comprise tubular and plate-like sectionswelded, brazed, or otherwise sealingly secured together, as shown, toprovide the required envelope parts.

The anode I3, which may be of any suitable or preferred structure, issupported within the envelope sleeve I5 on a shaft-like element 30, saidelement preferably comprising a tube which extends from the ano-dethrough the chamber 24 and outwardly thereof through the opening 28,said tubular shaft member being journaled for rotation in the bearingmeans 25.

The entire structure may conveniently be supported in operating positionon pedestals 3 I, comprising rods mounted on, and extending upwardly of,a suitable supporting base 32, the rods 3| carrying the flange structureI9 with closure means 2| sealingly clamped thereto.

The end of the shaft sleeve 3D, which projects outwardly of the closuremeans 2|, may be drivl is also preferably formed with a packing glandfor turnably receiving the terminal end of the member 30, the gland 35providing a liquid seal for connecting the open end of the member 30with conduit means 36. The base 32 may, also, be formed with a liquidconduit 3T connected with one end of a tube 38, `which extendsconcentrically within the tubular member 30, the

tube 33 opening, at its remote end, into a cavity 39 formed within thebody of the anode I3, said cavity communicating, also, with the anodeconnected end of the member 3|). By circulating a cooling medium, suchas water, through the cavity 39 by way of the conduits 36 and 3l and theconcentric tubes 30 and 38, the operating tempera-ture of the anode may.be held within safe limits.

In order to maintain desired low pressure, substantially vacuumconditions within the envelope, during operation of the generator, theclosure means 2| may be provided with a conduit 40 adapted forconnection with suitable exhaust that is to say, through the opening 28.To this end, the present invention contemplates the provision of novelvacuum seal means 4I, preferably arranged as a replaceable unit adaptedto be mounted on, and to form a part of, the envelope structure. Asshown, the seal means 4| comprises a housing 42 of preferably cup-shapedconfiguration, having flange means 43 at the lip of the cup member, saidflange being adapted to sealingly engage in the seat 21 formed on theclosure means 2|. To this end, the flange 43 may be secured on the seat21, as by means of clamping studs 44, a suitable sealing gasket 45 beingapplied and clampingly received between the flange 43 and the seat 2l.The bottom of the cup-like housing 42 is formed with a central opening46, sized to snugly, yet turnably, receive the shaft member 33, saidopening being preferably tted with a packing gland 41 around the shaft.The housing member 42 is preferably made of metal.

The cup-shaped housing 42 is, thus, adapted to define a chamber 48around the shaft member 30 at, and communicating with, the opening 28,and, thus, when mounted, comprises a part of -the envelope itself. Theseal comprises a pair of cooperating, preferably metal rings 49 and 50,one of which is mounted, or formed, on the shaft member 30 in ipositionproviding an annular sealing surface facing into the chamber 48, and theother of which is moimted on the cup-shaped housing 42 in positionproviding an annular sealing surface adapted to engage and form arunning seal with the sealing surface of the cooperating ring. One ofthe ring elements preferably comp-rises relatively hard material, suchas steel, while the other may comprise a relatively softer metal, suchas bronze. The more readily replaceable ring 49 is preferably made ofthe softer material to take the wear. One of the ring elements, also, isyieldingly supported, as on a metal bellows 5l, whereby the resilienceof said bellows may serve to hold the ring element in yieldingengagement with the cooperating ring element."v If desired, spring means52 may be employed to aid in holding the ring elements yieldingly inmutual sealing engagement.

If desired, the shaft mounted ring 50 may be, thus, yieldinglysupportedon the shaft in the manner shown in Fig. 3, wherein the shaft mountedring comprises an element 50' supported on the shaft by means of thebellows 5l and urged by the spring 52 into engagement with the seatelement 49 on the housing 42. It is preferable, however, as a matter ofmanufacturing convenience, to mount the ring 50 rigidly, and sealinglyon the shaft member 30, as shown in Fig. 2, as by welding, or brazing,or otherwise integrally fastening the ring 50 upon the shaft, preferablyin position extending in the opening 28, If desired, the shaft 3|) maybe integrally formed with a shoulder in the opening 28, in position tocooperatively engage the seal ring 49. In either case, the cooperatingannular surfaces of the ring or shoulder 50 and the seal ring 49 `arefinished accurately, to provide smooth, highly polished annular sealingsurfaces. The ring 49, also, is sealed, as by brazing the same in acentral opening formed in a metal plate 53, the plate, in turn, beingsealed, outwardly of the ring 49, to one end of the bellows element 5|.The other end of the bellows is sealed on a metal mounting ring 54,adapted to sealingly engage vin an annular seat 55 formed in thecup-shaped housing 42, the mounting ring being retained in its seat asby means of clamping rings 55, which may be threadingly secured in thehousing. The spring means 52 may comprise a helical spring element,encircling the shaft, and, as shown in Fig. 2, bearing at one end onthe seal ring 49,

the other end of the spring seating upon the bottom of the cup-shapedhousing around the opening 46. As shown in Fig. 3, however, the spring52 may bear at one end on the shaft mounted seal ring 50, the other endof the spring engaging a shoulder formedA on the shaft. .In thisconnection, the arrangement, as shown in Fig. 3, embodies a removablemounting nut 54' adapted for threaded, sealing engagement on the shaft,said nut providing an armular spring seat and a concentric annular rib,to which one end of the bellows element is sealingly secured,

the other end of the bellows element carrying the disk 53' on which theshaft supported seal ring 5U is sealingly mounted. In the Fig. 3embodiment, the cooperating seal ring 49' is sealed directly on themounting ring 54.

When the shaft 30 is rotating, the rings 49 and 59 will turn, one withrespect to the other, to form a running ground joint between thecooiperating seal faces of the rings, the rings being, at all times,maintained in tight sealing engagement by the action of the spring 52.The envelope will, thus, fbe sealed against fluid leakage around theshaft at the opening 28, since the ring 50 is sealed around the shaft,the ring 49 is sealed to the bellows, which, in turn, is sealed to thehousing 42, the housing 42, in turn, being sealed to t'he envelopeclosure member 2l, and the running ground joint sealing against leakagebetween the rings 49- and 50, as shown in Fig. 2. In theFig. 3embodiment, the envelope is sealed againstffiuid leakage since the ringv50 is sealed 6 to the bellows, which in turn is sealed to the shaft,while the ring 49' is sealed to the housing 42, the running ground jointsealing against leakage between the members 49' and 50'.

In order to enhance the efficacy of the seal, means is provided formaintaining a supply of a liquid sealing medium, such as oil, around theshaft 30 at, and outwardly of, the seal ring 49, said supply of liquidpreferably being contained within the space 51 defined around the shaftbetween the bottom of the housing 42 and the ring supporting means,comprising the disk 54,- bellows 5I, and disk 53. To this end, thehousing 42 is provided with conduit means 58 connect ing with an oilreservoir 59, whereby oil may be supplied to,` and held in, the space 51to completely ll the same up to the ring 49. In this connection, it isdesirable, also, though not absolutely essential, to connect thereservoir 59 with suitable exhausting means, so that the seal-- ingliquid in the reservoir 59 and the space 51 may be held under reducedpressure, to thus minimize any tendency for the liquid sealing medium toleak through the ground joint into the evacuated envelope.

It is thought that the invention and its numer` ous attendant advantageswill be fully understood from the foregoing description, and it isobvious that numerous changes may be made in the form, construction andarrangement of the several parts without departing from the spirit orscope of the invention, or sacrificing any of its attendant advantages,the forms herein disclosed being preferred embodiments for the purposeof illustrating the invention.

The invention is hereby claimed as follows;

l. An X-ray generator comprising means forming a sealed envelopeproviding a main chamber and a sleevelike extension, a cathode and a c0-operating rotatable anode mounted within the main chamber, a shaftmember drivingly connected with said anode and extending in saidsleevelike extension and outwardly thereof through a shaft opening insaid extension, means for sealing said opening against fluid leakagetherethrough along said shaft member, comprising a running seal andflexible partition means supporting the same in position forming aliquid chamber in said sleevelike extension, at the end thereof remotefrom said main chamber, and around said shaft at said opening, means formaintaining Aa supply of liquid sealing medium in said liquid chamber,and exhaust conduit means yconnected to said sleevelike extensionbetween said main and liquid chambers.

2. An X-ray generator comprising means forming a sealed envelopeproviding a main chamber and a sleevelike extension, a cathode and acooperating rotatable anode mounted within the main chamber, a shaftmember drivingly connected with said anode and extending in saidsleevelike extension and outwardly thereof through a shaft opening insaid extension, means for sealing said opening against fluid leakagetherethrough along said shaft member, comprising means defining a liquidchamber in said sleevelike extension, at the end thereof remote fromsaid main chamber, and around said shaft at said opening, means formaintaining a supply of liquid sealing medium in said liquid chamberunder substantial pressure of the order of atmospheric pressure, andexhaust conduit means connected to said sleevelike extension betweensaid main and liquid chambers to maintain low pres 7 sure conditions:therein .of the: orderapproaching am absolute: vacuum..

3.' An Xfray generaton comprisingmeansforming a sealed: envelopeprovidingza mainzchamber and.sleevelike-extensicn, aV cathode'and acooperating rotatable anodei mounted'. within the main. chamber, a shaftmemberdrivingly.l connected" with said anode andv extending in saidsleevelike extension and outwardlyv thereof throughza shaft opening insaidextension, means for sealing said opening'v against uid leakagetherethrough along said shaft member, compris'- ing:l meansforminguannular abutments on said shaft and on. said. envelopeextension. adjacent said'v opening, onev off said. abutments providinganxannular runningrseal seat, an. extensible bellows sealedatoneendonfche other-of saidzabut. ments, a seali ring sealingly secured onsaid bellows at the opposite. end` thereof lin position toV form:runningv engagement with said: seat, whereby to denne a liquid.chamberiin saidsleevelike extension around saidshaft'at said opening,means for maintaining asupply of liquidzsealing medium in saidi chamber,and. exhaust conduit means connected to said sleevelike extensionbetween said main and'liquid chambers.

4. Arr X-ray generator comprising means'forminga.y sealedenvelopeproviding aY main chamber and a sleevelike extension, ay cathodeanda cooperating rotatable anode mounted within the mainl chamber, ashaft member drivingly connected with. said anode and extending in saidsleevelikev extension and: outwardly thereof througha shaft openingj insaid extension, means for sealing said opening against fluidA leakagetherethroughalong; said shaft member, comprising meansTOrming` anannular running seal seat on saidshaft and an annular mounting abutmentonsaid envelopey extension adjacent said opening, an extensible-bellowssealed at oneend on the mounting abutment, a seal ring sealingly securedon. said bellows at the oppositeiend thereof in position toformI runningengagement with said seal seat, whereby to dene a liquid chamber insaidisleevelike extension around said shaft at said opening, means formaintaining a supply of liquid sealing medium in said chamber, andexhaust conduit means connected to said sleevelikev extension betweensaid main and liquid. chambers.

5. An -X-ray generator comprising' means forming a sealed envelopeproviding a main chamber anda sleevelike extension, a cathode'and acooperating rotatable anode` mounted within the main chamber, a shaftmember drivingly connected with. said anode` and extending in saidsleevelilse extension and outwardly thereof through a shaft opening insaid extension, means for sealing said opening against fluid leakagetherethrough along said shaft member, comprisingmeans forming an annularmounting abutment on said shaft and an annular running seal seat on saidenvelope extension adjacent said opening, an extensible bellows sealedat one end onthe mounting,.a seal ring sealing secured on said bellowsat the opposite endthereof in position to form running engagement" with'said seat, whereby to denne a liquid chamber in said sleevelikeextension around saidv shaft at'said opening, means for maintaining asupply of liquid sealing medium in said chamber, and exhaustY conduit Ichamber; anda sleevelike; a. rotatable element incsaimmain chamheraashaftimember' drivingly connected withsaidgelementiand exe tendinginsaid sleevelik'e extensionandputwardly thereof through: a.. shaftopeningv extene sion, .means for sealingfsaid opening againstfluidleakage. therethrough. along said shaft member, comprising arunning'seal andexible partition meanssupporting. the sameinpositionfomningra liquid chamberv int said sleevelike" extensiong. atthe end thereof remote from said main; chamber, and aroundfsaid shaft:at :said opening; ,means for:maintainingal supplyA of liquid sealingmedium inf. said. liquid chamben. and exhaust conduit meansconnectedi tosaid sleevelike extension betweensaidmain. and liquid chambers;`

A.. low pressure'. deviceA comprising means forming a sealedA envelopeproviding. a main chamber'` and a sleevelikelv extensioma` rotatableelementi inv said maiirY chamber, a shaft member drivingly. connected;with said element and extendingl in said-:sleevelike extension andoutwardly thereof. through a. shaft opening in said exten? sioruineansfor 'sealing said opening against fluid.

leakage" therethrough alongl said shaft. member; comprising` means'defining; a: liquid chamber:v in said sleevelike extension, at: the' endthereof remote.- from said. main chamber, andv around said shaft atsaid.y opening; means `for maintaining: a supply of liquid sealingmediumv inv said liquid chamber 'under substantial. pressureY of the.order ofi atmospheric pressure, and exhaust conduit means connected tovsaidsleevelikeextension be.- tweensaid main and liquidcharnbers toVmaintain low pressure conditions therein of the order appreaching. an.absolute vacuum.

8. A low pressure device comprising means forming asealed:envelope-providinga main chamber: and a sleevelike extension, arotatableelement said main chambera shaft membery drv; ingly connectedwith said element and extending in said sleevelike extensionandzoutwardlythereof through a shaftopeningin.saidextension, means forsealing said opening against fluid leakage therethrough along'saidshaftmemb'er; comprising means; forming annular abutments on said shaftand on said envelope. extension adjacent said. opening, one of saidabutmentsv providing an annular running seal seat,' an extensiblebellows sealed at one endonthe. other of .said abutments,'.a.seal ringsealingly secured on said bellows at. the. opposite. end. thereof in:position to formI running engagement withsaid seat; whereby .tozdene aliquid chambertinsaid: sleevelike'fex'- tension around saidv shaftw at.saidA opening, means for maintaining a. supply of( liquid sealing me'.-diuini inl said chamber, and exhaust conduit means connected to saidsleevelike extension be.- tween said main and liquid chambers.4

9. A low pressure device comprising means forming aisealed envelope'providing a main chamberxand. a sleevelike extension, a rotatable. ele.-Inent in said main' chamber, ashaft'member drivingly/connected'with saidelementv and extend.- ing insaid sleevelilie extension. and outwardlythereofthrough a shaftk opening insaid." extension; means. for sealingsaid. opening against uid leakage therethrough along said.sha-:ftLmembei-, comprisingv means formingr an .annular ruiming seal`seat onsaid shaft'andiant annular: mount;

abutment on said' envelopeY extensiona'dja'- cent said opening, anextensible bellows sealed atone endronthe: mounting abutment, a sealring sealingly secured.onsaidbellows'at the opposite end therenfgin'.positonito: form running e engagesment: withgsaidseal seat;v whereby'to;deneia' liquid chamber in said sleevelike extension around said shalt atsaid opening, means for maintaining a supply of liquid sealing medium insaid chamber, and exhaust conduit meansnconnected to said sleevelikeextension between said main and liquid chambers.

10. A low pressure device comprising means forming a sealed envelopeproviding a@ main chamber and a sleevelike extension, a rotatableelement in said main chamber, a shaft member drivingly connected withsaid element and extending in said sleevelike extension and outwardlythereof through a shaft opening in said extension, means for sealingsaid opening against fluid leakage therethrough along said shaft member,comprising means forming an annulfar mounting abutment on said shaft andan annular running seal seat on said envelope extension adjacent saidopening, an extensible bellows sealed at one end on the mounting," aseal ring sealingly secured on said bellows at the opposite end thereofin position to form running engagement with said seat, whereby to dene aliquid chamber in said sleevelike extension around said shaft at saidopening, means for file of this patent:

maintaining a supply of liquid sealing medium in said chamber, andexhaust conduit means connected to saidsleevelike extension between saidmain and liquid chambers.

JOHN JOSEPH VLACH.

REFERENCES CITED The following references are of record in the 'l OTHERREFERENCES Lubrication in Vacuum by Vaporzed Thin Metallic Films, by Z.J. Atlee, J." T. Wilson, and J. C. Filmer, Vacuum Tube EngineeringDept., General Elec. X-Ray Corp., Chicago, Illinois (Rec. Apr. 15,1940). Reprinted from Journal of Applied Physics, Vol. 11, No. 9,611-615, Sept. 1940.

